1. Technical Field
The present invention relates to an optical reflecting device used in an image projection device such as a head-up display and a head-mounted display.
2. Background Art
Recently, an optical reflecting device for scanning with a laser beam and projecting an image on a screen or the like using a micro electro mechanical systems (MEMS) technology has been developed. In order to project an image, a two-dimensional scan with a laser beam needs to be performed using the optical reflecting device. As a method of driving the optical reflecting device, a piezoelectric actuator is employed, for example.
FIG. 15 is a perspective view of conventional optical reflecting device 1. Optical reflecting device 1 includes mirror part 9, fixed part 3 supporting mirror part 9, a pair of vibrating beams 4, and piezoelectric layers 10 for rotating mirror part 9. Each vibrating beam 4 couples mirror part 9 to fixed part 3 so that mirror part 9 rotates with respect to fixed part 3. When piezoelectric layers 10 are energized, they expand or contract. Due to this expansion or contraction, vibrating beams 4 are twisted to rotate mirror part 9.
Each vibrating beam 4 includes torsion bar 6 extending from mirror part 9, driving member 7, and a pair of elastic members 8. Driving member 7 is connected to the end of torsion bar 6 on the opposite side to mirror part 9. The pair of elastic members 8 are disposed closer to mirror part 9 than driving member 7, and face each other via the rotation center axis of mirror part 9. A first end of each elastic member 8 is connected to driving member 7, and a second end thereof is connected to a part of fixed part 3. The piezoelectric actuator of this application is disclosed by Japanese Patent No. 4285568, for example.